Ultraviolet (UV) light is found beyond the violet end of our visible spectrum of light, toward the X-rays. It is given off by the sun and is harmful to living things, which is why we need to wear sunscreen when we go out in the sun. Fortunately for us, most of it is absorbed by Earth's atmosphere.
Ultraviolet light from places other than the sun can tell us a great deal about the universe—specifically about stars that are between twice and ten times the temperature of the sun. Because Earth's atmosphere gets in the way, astronomers find it hard to see them. By the mid-1960s, however, humans were journeying beyond Earth's atmosphere...
Normal cameras pick up only light around the visible spectrum, but on November 11, 1969, astrophysicist Dr. George Carruthers [b. 1939) was granted a patent for an "Image converter for detecting electromagnetic radiation especially in short wave lengths." The far- ultraviolet camera was a 3-inch (7.62 cm), 48.5-pound (22 kg), gold-plated apparatus that could see stars that are a hundred times fainter than those that can be seen with the human eye. The camera was sent up with the Apollo 16 mission in 1972 and placed on the Moon's surface, allowing researchers to examine Earth's atmosphere for concentrations of pollutants. It recorded nearly 200 images, giving astronomers data on over 550 stars, nebulae, and galaxies, as well as providing new views of Earth. The camera looked into the ionosphere (the highest part of our atmosphere) and gave us some of our earliest solid data on the concentrations of man-made pollutants.
